The site gives you some direction as to viewing these files by installing AlternaTIFF: http://www.alternatiff.com/ and/or quicktime.
I have installed both of the aforementioned products and tested to no avail.
I have tested using IE7 and Firefox3, I have also tested whilst connected via the company network and via a 3G card and still nothing.
The website states "PTO cannot and will not provide direct user support for TIFF image
display or printing beyond the provision of hyperlinks to known suitable
free TIFF browser plug-ins."